1. Field of the Invention
The present invention relates to a one way clutch which is incorporated between a driving shaft and a driven shaft of e.g. motor vehicle, general industrial machine, etc., and has a function of transferring only power in a one way rotation of the driving shaft to the driven shaft.
2. Description of the Related Art
Conventionally, a one way clutch is provided with a retainer for receiving a sprag intervening between an outer ring and an inner ring. The sprag is pushed by a ring-shaped spring from outside toward inside in a radial direction of the retainer so that it is held by the retainer.
An example of the retainer is a retainer 30 as shown in FIG. 27.
The retainer 30 has a plurality of sprag receiving grooves 32 cut in an axial direction from the one end of an cylindrical structural body 31. Sprags (not shown) are mounted in the respective sprag receiving grooves 32.
The one way clutch is required to shorten its axial length for the purpose of miniaturizing. Therefore, the wall thickness (T1) of a remaining portion 33 formed by the sprag receiving grooves 32 of the retainer 30 must be reduced.
However, the one way clutch provided with the retainer with the remaining portion having a reduced wall thickness has the following defects.
(1) Since the wall thickness of the remaining portion is small, the strength of the retainer is lowered. Therefore, while the retainer is used for a long time, the remaining potion will suffer from damage such as crack. Thus, the retainer is likely to be not able to effect smooth operation.
(2) When the sprag slips owing to excess load, it vigorously hits on the retainer. Therefore, while the retainer is used for a long time, the remaining portion will suffer from damage. Thus, the retainer is likely to be not able to effect a smooth operation.
(3) If the wall thickness of the remaining portion is increased so that the remaining portion does not suffer from damage, the elasticity of the retainer is reduced and its size will be increased, thereby making it impossible to miniaturize the one way clutch.